1. Field of the Invention
The present invention relates to a method for water electrolysis, and particularly to a method for water electrolysis using an anode having a low oxygen overvoltage and superior durability.
2. Description of the Prior Art
In view of the recent energy shortage, attention has been drawn to hydrogen as a new energy source replacing petroleum. Industrial methods for the production of hydrogen are generally classified into electrolysis of water and gasification of cokes or petroleum. The electrolysis of water has an advantage that the starting material, i.e. water is readily available, but it has at the same time various difficulties such as the requirement of equipment for electrolysis, the fact that the electrolytic solution is readily degraded by carbonation, and that a large installation area and high costs are required for installations. On the other hand, the gasification of cokes or petroleum usually involves cumbersome operations and requires a large scale installations thus leading to high installation costs.
In an attempt to overcome the above difficulties, it has recently been proposed to produce hydrogen by electrolyzing water in an electrolytic cell wherein a cation exchange membrane is utilized.
It is known to use so-called ion exchange membrane electrolysis for electrolysis of sodium chloride (brine). However, in the electrolysis of water which is conducted by supplying an aqueous alkaline solution such as an aqueous solution of e.g. potassium hydroxide to an anode compartment partitioned by a cation exchange membrane and supplying water or a dilute aqueous alkaline solution to the cathode compartment, the conditions of the anode compartment are quite different from the conditions of the anode compartment in the electrolysis of sodium chloride. Nickel is considered to be particularly useful for an anode used under such an alkaline condition.
On the other hand, an anode made essentially of a noble metal such as platinum, palladium or ruthenium, or an alloy or oxide thereof which is used in the conventional electrolysis of sodium chloride, is not practically useful as an anode for the electrolysis of water because of the following problems.
Namely, ruthenium and palladium tend to be gradually dissolved by the effect of the alkaline solution and thus they are inferior with respect to durability.